LIFE HISTORY OF NANOS VIETTEI (PAULIAN, 1976) (COLEOPTERA:SCARABAEIDAE: CANTHONINI), A REPRESENTATIVE OF AN ENDEMIC CLADE OF DUNG BEETLES IN MADAGASCAR

摘要

Nanos viettei (Paulian, 1976) is a nocturnal generalist dung beetle mostly feeding on carrion. Despite its relatively small size (6 mm), N. viettei is a long–lived (up to two years) species with extremely low life-time fecundity (maximum four offspring) and very low mobility (based on mark-recapture studies). Matings are promiscuous and, exceptionally for Canthonini, males typically guard the female for at least several hours after mating. There is no bisexual cooperation or mate courtship unlike in many other Scarabaeidae. Heterospecific copulation was observed in captivity, supporting the hypothesis of genetic introgression between closely related species for which there is some molecular evidence. Hybridization and low hybrid fitness may at least partly explain the exclusive geographical ranges of species in the `viettei species-group'.